In general, differing from a wired channel environment, a radio channel environment in a communication system receives distorted signals through the real transmission signals because of many factors such as multipath interference, shadowing, attenuation, and time-varying noise and interference. In this instance, fading caused by the multipath interference relates to a reflector or a user, that is, a mobile terminal of a mobile station, and the mobile terminal receives signals that are a mix of the real transmission signals and interference signals.
Therefore, the received signals are substantially distorted real transmission signals and they degrade performance of the entire wireless communication system. Resultantly, the fading phenomenon can distort the amplitude and the phase of the received signals, and is a main factor generating a problem in high-speed data communication in the radio channel environment. Many studies have been progressed so as to solve the fading phenomenon, one of which is the multiple-input multiple-output (MIMO) system.
The MIMO system uses multiple antennas in the transmitting/receiving part to generate a plurality of independent fading channels and transmits different signals for the respective transmit antennas, thereby substantially improving the data rates. However, the MIMO system is weak in inter-symbol interference of transmission signals generated by high data rates and frequency selective fading. In addition, a precoder is used to perform a predetermined precoding process on the transmission signals so as to eliminate the influence of signal interference among multiple users, but the power difference between the signal interference and the transmission signal is increased to deteriorate the signal-to-noise ratio (SNR), generating performance degradation.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.